Turn the caps off..
The later 8 cylinder engines are V8's not straight eights.

You can drop a later twin cam into your car easily. just use the mount arms off your original engine. The later engine has a block layout that is very similar. The manual trans are the same part. If you have manual trans six ,drop it in.
Generally I wouldn't advise using a 280 S,the injected engines are more powerful and easier to keep tuned.
The V8's go in easily too but again you need to swap over the mount arms.
When doing the swap,have your donor car close by so you can use things like the igntion circuit ,radiator hoses etc.